A perspective on Quality-by-Control (QbC) in pharmaceutical continuous manufacturing.

The Quality-by-Design (QbD) guidance issued by the US Food and Drug Administration (FDA) has catalyzed the modernization of pharmaceutical manufacturing practices including the adoption of continuous manufacturing. Active process control was highlighted recently as a means to improve the QbD implementation. This advance has since been evolving into the concept of Quality-by-Control (QbC). In this study, the concept of QbC is discussed, including a definition of QbC, a review of the recent developments towards the QbC, and a perspective on the challenges of QbC implementation in continuous manufacturing. The QbC concept is demonstrated using a rotary tablet press, integrated into a pilot scale continuous direct compaction process. The results conclusively showed that active process control, based on product and process knowledge and advanced model-based techniques, including data reconciliation, model predictive control (MPC), and risk analysis, is indispensable to comprehensive QbC implementation, and ensures robustness and efficiency.

Continuous direct compression of a commercially batch-manufactured tablet formulation with two different processing lines.

The transfer from batch-based to continuous tablet manufacturing increases the quality and efficiency of processes. Nonetheless, as in the development of a batch process, the continuous process design requires optimization studies to ensure a robust process. In this study, processing of a commercially batch-manufactured tablet product was tested with two continuous direct compression lines while keeping the original formulation composition and tablet quality requirements. Tableting runs were conducted with different values of process parameters. Changes in parameter settings were found to cause differences in tablet properties. Most of these quality properties could be controlled and maintained within the set limits effortlessly already at this stage of studies. However, the API content and content uniformity seemed to require more investigation. The observed content uniformity challenges were traced to individual tablets with a high amount of API. This was suspected to be caused by API micro-agglomerates since tablet weight variability did not explain the issue. This could be solved by adding a mill between two blenders in the process line. Overall, this case study produced promising results with both tested manufacturing lines since many tablet properties complied with the test result limits without optimization of process parameter settings.

Challenges encountered in the transfer of atorvastatin tablet manufacturing - commercial batch-based production as a basis for small-scale continuous tablet manufacturing tests.

As is the case with batch-based tableting processes, continuous tablet manufacturing can be conducted by direct compression or with a granulation step such as dry or wet granulation included in the production procedure. In this work, continuous manufacturing tests were performed with a commercial tablet formulation, while maintaining its original material composition. Challenges were encountered with the feeding performance of the API during initial tests which required designing different powder pre-blend compositions. After the pre-blend optimization phase, granules were prepared with a roller compactor. Tableting was conducted with the granules and an additional brief continuous direct compression run was completed with some ungranulated mixture. The tablets were assessed with off-line tests, applying the quality requirements demanded for the batch-manufactured product. Chemical maps were obtained by Raman mapping and elemental maps by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Large variations in both tablet weights and breaking forces were observed in all tested samples, resulting in significant quality complications. It was suspected that the API tended to adhere to the process equipment, accounting for the low API content in the powder mixture and tablets. These results suggest that this API or the tablet composition was unsuitable for manufacturing in a continuous line; further testing could be continued with different materials and changes in the process.

Parameter optimization in a continuous direct compression process of commercially batch-produced bisoprolol tablets.

Continuous tablet manufacturing is a competitive option to replace the traditional batch manufacturing approach. The aim of this study was to evaluate technology transfer from batch-based direct compression of a commercial tablet formulation to continuous direct compression without changes to the composition of the formulation. Some powder studies were conducted with the raw materials and multi-tip punches were utilized in the tableting studies. To lower the high level of tablet weight variability that was evident during preliminary tests, a process parameter optimization was performed using an experimental design with different rpm values of force feeder and mixer impeller. By selecting the most appropriate settings of these parameters for the studied product, the weights of the tablets could be controlled adequately to meet the specification criteria. The functionality of the best-performing parameter settings was investigated with a three-hour-long tableting run. The tablets were evaluated with the same quality criteria as the commercial batch-produced tablets, and they passed all the tests performed in this study. Despite the challenging material properties according to the flowability tests, production of tablets with the desired quality was achieved using the original composition with continuous direct compression.

Effect of material properties on the residence time distribution (RTD) of a tablet press feed frame.

In continuous manufacturing (CM) of pharmaceutical tablets, the residence time distribution (RTD) of the tablet press feed frame plays an important role in ensuring the critical quality attributes (CQAs) of the final product. Knowledge of factors affecting the RTD of the feed frame is necessary for sufficient RTD model development. The aim of this work is to investigate the effect of material properties on the mean residence time (MRT) and the lag time. Seven materials with different powder properties were used and the tracer concentration as a function of time were obtained. The RTD model obtained by tracer experiments is approximated using a plug flow reactor (PFR) and a continuous stirred tank reactor (CSTR). The loading plots of principle component analysis (PCA) indicated that the powder bulk density is correlated with the RTD model parameters. Therefore, we focus on establishing the relationship between the bulk density and the MRT. As a result, a linear correlation is obtained to describe the relation between the MRT and the powder bulk density. The simulated results show that the material with lower bulk density had higher risk of producing out-of-specification (OOS) products in comparison to higher bulk density powders.